Big Sis sought out my dick only when she wasn't feeling horny. Because she has a libido that rivals mine and our Mother's, she asked for a 'treatment' about three times a week. It was like I was her therapist but without the fat payments.
"Mom is keeping a sharper eye on us since she learned we were not-boinking."
"I'm not worried." I was slowly jerking myself, sitting on my bed while she knelt before me. I had been doing it for ten minutes. My big sister always tried to talk about non-sexy things, to bolster her boredom.
If she was trying to bore me, she failed big time. Mom's envy for Nell's access to my dick was cutting dangerously into Dad's sleep! Mom would either be on top, boning him, or beside him, running her vibrator late into the night.
What Nell didn't know, I was tracking Mom's sexual arousal cycle. Poor Mom was about to hit her monthly peak. I wanted to be ready for it!
"Ohh, yeaaahhh! I shouted and cum erupted from my prick!" My mommy complex was my favorite way to reach the big O, but I had to restrict using it. Opposite of Nell's goal, I never wanted to get bored of fantasizing about Mom.
Nell had learned to stay three feet from the tip of my prick, or she'd get soaked. Each time her body or clothes caught flying spunk, she would scurry away, angry as fuck but not at me. I'd made her promise not to blame me for accidents.
My cum arced over the carpet and crashed against the plastic sheet I'd placed between us. It had a circular target painted on it. When my spurts ended, and the last only oozed out of the tip, she tallied the impacts.
"Seventeen." She looked up at me grunted. "Are you even trying to score?"
Oh yeah I was - her. It was as good a moment as any to ask. "Are you sure you're not going to your room and masturbating after watching me?" For a while now, I hadn't seen her get even slightly aroused by my cock's towering presence. That however might be a testament to her stoic facade.
Nell shuffled on her toes and knees. "I've had setbacks. Frankly it's none of your business."
"I guess not, but I would like to know if your crazy scheme is actually working."
My proud sister pursed her lips. She fumed, just as mother had, dozens of days earlier. "You ought to be plenty satisfied with your ravishing sister kneeling while you jerk off."
"Not too long ago, you were showing me your tits."
"I'm not proud of that." Nell's behavior during our sessions had certainly changed. Whether it reflected her success or mine I couldn't fathom.
"Then are we done here?" My hand grabbed the zipper tab hanging under my ball sack.
"I-I guess."
"If you stay over an hour, I'm gonna have to charge you double." I grinned.
"Maybe a little longer." Nell surprised me. "Can you get it hard again?"
"Can you show me your tits?"
My big sister actually blushed! She would rather I watched porn with better tits than hers, while jerking off for her, but she'd never admit to being inferior.
The sight of red tinge on my sister's cheeks was already sending blood into my dangling 8 inches. But I had pushed her far enough. I made a new offer. "How about if you hold it, or maybe rub it a little?" I let go of my soft length.
"I-I've seen enough for today." Her voice quivered so slightly. Only people who've lived with her for eighteen plus years would have noticed.
I leaned back and carefully zipped up my happy penis. "Good session."
"Fuck you." She said that a lot before ending a 'session.' I wondered if the phrase signaled anything useful. Perhaps after telling me off, she finger-fucked herself back in her room. Or perhaps Nell masturbated when she didn't curse. She left my room. I set a twenty second timer.
Twenty five seconds later, my ear was pressed to her door. I nodded at what I heard. "After she says it. Definitely." I almost laughed the words loudly.
"Definitely what?" Mom stood at the end of the hallway, wearing her tool belt.
"Uh, um." I cleared my throat and stood straight, stepping wide from Nell's bedroom door. "I'm definitely not spying here."
"Hear anything good?"
"It was very good."
"For her or for you?"
"I never spy and tell."
She shook her head and ambled over. She brushed me aside, marching to her room.
I dallied at Nell's door, not listening. I had heard what I wanted. If my sister was getting bored of my big cock, she was fantasizing about something else to make long moans and sharp heaves of breath. I should have walked away, patting myself on the back. Intuition kept me in the hallway, waiting.
A glance at my parents' bedroom door gave me a clue. I was sure Mom had closed it, but now it was open enough for a horny minded son to peep through. Six big steps put me three feet away from the door. "Mom, you left your door open."
"It wasn't an accident." She replied just loud enough to reach me.
My mind sank further into the gutter. It was her tone, not her volume that compelled me. "You don't mind me looking in." I warned.
"I don't want to be a hypocrite."
My brain managed to gather enough synapses to puzzle out what she meant. I nearly leaped to plant my face at the door's opening.
I hadn't missed the main event. She was pulling down her boxers. Panties would have chaffed her crotch, given the kind of work she performed. My dick scraped up the inside of my trousers, saluting my naked mother. I winced, but I didn't care. Ask most people, and they'll tell you that my sister is sexier and prettier than Mom. Not by much, but only I think that's horseshit. Mom has bigger tits and a bigger ass, but Nell is curvier by proportions. Maybe it's just me, but my mother's little belly bulge alone would have brought my dick to full mast.
It's not like she stood posing naked for me. She ambled into the master bath, again leaving its door slightly open. I slipped into the bedroom and crept up to that view.
Mother tied her hair, arms raised, her large, soft but not quite sagging breasts staring at me in the mirror. Two mommy-boobs and the thatch of dark brown cut off by the mirror's bottom edge, urged me to pull out my dick and wank like a proper Peeping Tom.